For criminal conduct, you should always contact the police. Landlords do not have police powers.
Depending on the nature of the disturbance, your landlord does have an obligation to control tenants and provide a safe living environment. If the disturbances become to frequent, the city will sometimes bring charges against landlords. Your remedies would include continued reports to the police, a complaint to the rent control board in your area (if there is one), complaint to the health department, a complaint to the city, or demanding that the landlord let you out of your lease.
The law is the law of nuisance. (California Civil Code section 3479, et seq.)
In addition, each city usually has its own noise ordinance.
The agency is your local police department, as well as your city's Code Enforcement Unit.
Frank W. Chen has been licensed to practice law in California since 1988. The information presented here is general in nature and is not intended, nor should be construed, as legal advice. This posting does not create any attorney-client relationship with the author. For specific advice about your particular situation, consult your own attorney.